1. Field of the Invention
The present invention relates generally to an apparatus and method for transmitting packet data in a CDMA (Code Division Multiple Access) mobile communication system, and more particularly an apparatus and method for providing multimedia broadcast/multicast services.
2. Description of the Related Art
With the development of the communication industry, services provided by a CDMA (Code Division Multiple Access) mobile communication system has developed multimedia multicasting communication services capable of transmitting large-capacity data, such as packet data and circuit data, as well as voice services. A broadcast/multicast service capable of providing data from one data source to a plurality of pieces of UE (User Equipment) to support multimedia multicasting communication has also been suggested. The broadcast/multicast service is divided into a CBS (Cell Broadcast Service) mainly based on messages, and an MBMS (Multimedia Broadcast/Multicast Service) for supporting various types of multimedia, e.g., real-time video and voice, still images, characters, etc.
The CBS is used to broadcast a plurality of messages to all pieces of UE located in a specific service area. At this time, the specific service area in which the CBS is provided can be one small cell or an entire service area in which a mobile communication service is provided. A service area can also be set by each broadcast message.
FIG. 1 illustrates a CDMA (Code Division Multiple Access) mobile communication system for providing a conventional CBS. Referring to FIG. 1, CBEs (Cell Broadcast Entities) 101, the sources of all cell broadcast messages, are devices for providing specific messages, e.g., weather information on a regional basis. The CBEs 101 can exist as a plurality of devices based on types of services provided in a mobile communication network. CBE messages from the CBEs 101 are transferred to a CBC (Cell Broadcast Center) 103 through a predetermined interface 102. The interface 102 between the CBEs 101 and the CBC 103 can vary with a mobile communication carrier or CBS provider. Further, the interface 102 is not limited to a certain specification. The CBC 103 manages the CBE messages provided from the CBEs 101 on the basis of a predetermined system, and a CBS message corresponding to a CBE message is transferred to an RNC (Radio Network Controller) 105.
More specifically, the CBC 103 selects cells to which the CBS message is transferred, creates a CBS message based on the CBE message, and transmits the created CBS message to the RNC 105. The RNC 105 decides, for example, a point of time for broadcast, and the number of an iterative transmission for the CBS message, at the time of broadcasting the CBS message. That is, the CBC 103 executes an overall control operation for the CBS. The CBS message created by the CBC 103 is transferred to the RNC 105 through a predetermined interface IuBC 104. The CBS message transferred to the RNC 105 is stored in the RNC 105. The RNC 105 sets up an Iub interface 106 between itself and Node-Bs 107, and a Uu interface 108 between pieces of UE (User Equipment) 109 and the Node-Bs 107.
To set up the interfaces, the RNC 105 considers a size of the CBS message and a radio channel condition on a cell basis. Setup information is transferred to the UE 109 through radio bearers. The RNC 105 carries out a CBS message storage function, a radio bearer setup function, a CBS message scheduling function, reporting to the CBC 103, state information indicating whether the transmission has succeeded or failed, etc. The UE 109 receives the CBS message, processes an error of the CBS message, and transfers the received CBS message to a higher layer, etc.
FIG. 2 is a flow chart illustrating signal processing based on a “Write-Replace” procedure as one of elementary procedures of the IuBC interface 104 between the CBC 103 and the RNC 105 when the CBS is provided.
Referring to FIG. 2, the elementary procedures of the IuBC interface 104 consist of five procedures including: a “Write-Replace” procedure for transferring a CBS message, a “Kill” procedure for stopping the CBS message, a “Load Status Enquire” procedure for enquiring the amount of load of the CBS message, and a “Reset” procedure for terminating the broadcast in one or more service areas. At step 203, the “Write-Replace” procedure is used when the CBC 103 transfers a new CBS message to the RNC 105 or changes a previously transmitted CBS message. In the “Write-Replace” procedure, the CBC 103 transfers a WRITE-REPLACE message carrying the broadcast information to the RNC 105. The RNC 105 stores the content of the received WRITE-REPLACE message and performs the predetermined processing. At step 204, the RNC 105 terminates the “Write-Replace” procedure by transmitting a response message based on a result of the performed processing. The response message includes a “WRITE-REPLACE COMPLETE” message indicating the successful outcome of the procedure and a “WRITE-REPLACE FAILURE” message indicating the unsuccessful outcome of the procedure.
Also, the WRITE-REPLACE message commonly includes information relating to a message type, a message ID (Identifier), a new serial number, an old serial number, a service areas list, a category, the number of broadcasts, a repetition period, a data coding scheme and broadcast content, etc. The message type indicates a message type based on each procedure, and the message ID identifies the message. The message serial number indicates a sequence number of the CBS message content. The entire message content is actually divided into a plurality of messages and then transmitted in the form of the messages. The new serial number is information indicating the new CBS message content. The previous serial number is used in when the CBS message is changed. The service areas list is information indicating at least one service area in which the CBS message is broadcast. The category is for identifying a priority of the CBS message content. The number of broadcasts and the repetition period is information indicating the number of broadcasts of the CBS message content and the repetition period of the CBS message content. The data coding scheme indicates a coding scheme on a language basis, and the actual CBS message content is contained in the broadcast content.
Using the elementary procedures, the CBC 103 can transfer the CBS message to the RNC 105 and control the broadcast for the UE 109.
FIG. 3 illustrates communication protocol architecture of a UTRAN (UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access Network) including the RNC 105 and the Node-Bs 107 illustrated in FIG. 1. Referring to FIG. 3, CBS information 301 in a U (User)-plane from the CBC 103 is transferred to a BMC-SAP (Broadcast/Multicast Control-Service Access Point) 302 via the IuBC interface 104. The BMC-SAP 302 transfers the CBS information 301 to a BMC layer 303 associated with a corresponding cell on the basis of a service area. Each of BMC layers 303 exists corresponding to one cell and broadcasts the CBS message to the corresponding cell. The CBS information 301 transferred from the CBC 103 is stored in the BMC layer 303 of the corresponding cell. The BMC layer 303 considers a length of the CBS message, the number of an iterative transmission, a repetition period, etc., and then requests an RRC (Radio Resource Control) layer 304 to set up or change radio channels through a C-SAP (Control-Service Access Point) 305. The RRC layer 304 controls radio resources of the RNC. In response to the radio channel setup or change request, the RRC layer 304 determines whether corresponding radio channels can be set up or changed. If the setup or change of the radio channels for broadcasting the CBS message cannot be achieved because of insufficient radio resources, the RRC layer 304 notifies the BMC layer 303 that the channel setup or change has failed. If the BMC layer 303 receives the notification of the channel setup or change failure from the RRC layer 304, it transmits the notification to the CBC 103. In response to the notification, the CBC 103 can adjust the length of the CBS message.
When the channel setup or change can be achieved, the RRC layer 304 configures an RLC (Radio Link Control) layer 307, an MAC-c/sh (Medium Access Control-common/shared) layer 309, and a Cell_PHY (Cell_PHYsical) layer 312 being a physical layer of a corresponding cell. Further, the CBS message is stored in the BMC layer 303 and then transmitted to the RLC layer 307 in a UM (Unacknowledged Mode) after considering the number of an iterative transmission, the repetition period, etc. and scheduling the CBS message. The RLC layer 307 operates in three modes including a TM (Transparent Mode), the UM, and an AM (Acknowledged Mode). The TM enables the RLC layer 307 to transparently transmit a data block from a higher layer to a lower layer without a header. The UM segments a data block received from a higher layer into RLC protocol data units having a predetermined size and then transmits header information such as a sequence number along with the RLC protocol data units. The AM segments a data block received from a higher layer into RLC protocol data units and adds header information to the RLC protocol data units. Moreover, the AM retransmits data in order to ensure error-free transmission. Since the same information is transmitted to a plurality of users in the broadcasting of the CBS message, the RLC layer 307 uses the UM because information retransmission is not possible.
The CBS message processed by the RLC layer 307 on the basis of RLC protocol data units having a predetermined size is transferred to the MAC-c/sh layer 309 through a CTCH (Common Traffic CHannel) 308 being a logical channel. The MAC-c/sh layer 309 transfers the received CTCH message to a Cell_PHY layer 312 of a corresponding cell. The MAC layer includes the MAC-c/sh layer 309 for a common channel and a MAC-d (Medium Access Control-dedicated) layer 310 for a dedicated channel on a UE basis. However, in the case of the CBS, broadcasting is achieved through an FACH (Forward Access CHannel) 311 being a common transport channel. Thus, the MAC-c/sh layer 309 transfers the CTCH message based on the CBS to the Cell_PHY layer 312 of the corresponding cell. The RRC, BMC, and RLC layers 304, 303, and 307, and the MAC layer are located within the RNC 105.
Also, the Cell_PHY layer 312 corresponding to each cell is located in the Node-B 107 and physically isolated from other layers. Thus, as an interface for safely transferring data is needed, the MAC-c/sh layer 309 uses the lub interface 106 to transfer data to the Cell_PHY layer 312. The Cell_PHY layer 312 corresponding to each cell performs channel coding, rate matching, interleaving, modulation, etc. for the CBS message distributed by the MAC-c/sh layer 309, maps the FACH to an S-CCPCH (Secondary-Common Control Physical CHannel) 313, which is a physical channel, and transmits the CBS message to a radio channel. Conceptually, mapping to the physical channel means that the CBS message is transmitted through a radio channel (Uu) 314.
FIG. 4 illustrates a detailed configuration and functions of the BMC layer 303 illustrated in FIG. 3. Referring to FIG. 4, a CBS message received from the CBC (Cell Broadcast Center) 103 is distributed or transferred from the BMC-SAP 302 to BMC layers 303, which correspond to all cells included in the entire service area. The BMC layers 303 transmit the CBS message to controllers 404. A controller 404 stores the received CBS message in a message storage 407. Further, if the CBC 103 considers information associated with the number of rebroadcasts, the repetition period, etc., received from the CBC 103 and then determines that the radio channels must be setup or changed, the CBC 103 requests the RRC layer 304 to perform the channel setup or change through a CBMC (Control BMC)-SAP 305. The operation of the RRC layer 304 has been described in connection with FIG. 3 above.
The CBS message stored in the message storage 407 is transferred to a scheduler 408 under the control of the controller 404. The scheduler 408 schedules the CBS message transferred from the message storage 407 and then transfers it to a transmission buffer 409. The CBS message transferred to the transmission buffer 409 is transferred to the RLC layer 307 through the UM 410. The RLC layer 307 corresponds to the same cell as the BMC layer 303.
FIG. 5 illustrates communication protocol architecture of a UE (User Equipment) for providing the conventional CBS corresponding to the configuration illustrated in FIG. 3. Referring to FIG. 5, the CBS message transmitted from the Node-B 107 through a radio channel is transmitted to a UE_PHY layer 503 of the UE 109 through an S-CCPCH 502 coupled to the Uu interface 314, which is a radio channel interface. The UE_PHY layer 503 carries out demodulation, deinterleaving, channel decoding, etc., for the received CBS message and then the CBS message is recovered to data on an FACH 504 being a transmission channel. The recovered data is transferred to a MAC-c/sh layer 505. A MAC-d layer 506, which is responsible for a dedicated channel, also exists in the UE side. However, the CBS message is not transferred to the MAC-d layer 506. The MAC-c/sh layer 505 transfers data corresponding to the CBS message to an RLC layer 508 responsible for a CTCH 507 being a corresponding logical channel. The RLC layer 508 associates CBS message segments having a predetermined size from the RLC layer of the RNC 105 to generate an original message and then transfers the associated CBS message segments to a BMC layer 509. The BMC layer 509 determines whether the CBS message from the RLC layer 508 is a new message or a repeated CBS message. If the CBS message is a new message, it is transferred to a higher layer through a BMC-SAP 510 as indicated by a reference numeral 511. An RRC layer 512 in the UE side controls the BMC layer 509 through a C-SAP 513, and controls the RLC layer 508, the MAC-c/sh layer 505 and the UE_PHY layer 503 through a corresponding C-SAP 514.
The above-described CBS provides information in the form of a CBS message to a user, but it does not provide the user with information in the form of various multimedia, such as a moving picture, a still image, voice and characters. Thus, an MBMS (Multimedia Broadcast/Multicast Service) is needed to provide a plurality of users with the information in the form of various multimedia. The operation of the MBMS is similar to that of the above-described CBS. However, the MBMS independent of the CBS provides information in the form of multimedia having high-speed data.
FIG. 6 illustrates a CDMA mobile communication system for providing a conventional MBMS. The MBMS must provide various multimedia contents. Thus, the system for providing the MBMS must accommodate a plurality of different content providers.
Referring to FIG. 6, each content provider 601 transfers data of multimedia contents to a BM-SC (Broadcast/Multicast-Service Center) 602. A predetermined interface 603 is coupled between the content providers 601 and the BM-SC 602. The interface 603 may vary with a communication network carrier or MBMS provider, and is not limited to a certain specification.
The BM-SC 602 schedules multimedia contents provided from the plurality of content providers 601 on a channel basis and then transfers the scheduled multimedia contents to a GGSN (Gateway GPRS Support Node) 605. Further, the BM-SC 602 provides an interface coupled to the content providers 601 and also carries out charging and authentication procedures for the content providers 601.
Alternatively, the data of the multimedia contents is not transferred to the BM-SC 602 and can be provided from a BMS (Broadcast/Multicast Source), which is a source providing entity directly coupled to the GGSN 605. Where the BMS 604 is allowed, an interface between the GGSN 605 and the BM-SC 602 or the BMS 604 can use an IP (Internet Protocol) 606. Alternatively, if the BMS 604 is not allowed, the BM-SC 602 manages all sources for the MBMS. Moreover, the BM-SC 602 uses a GTP (Generic Tunneling Protocol) 608 between the GGSN 605 and an SGSN (Serving GPRS Support Node) 607 to directly transfer the data of the MBMS contents to the SGSN 607, through the GGSN 605. The GGSN 605 copies the data of MBMS contents to transfer the copies to a plurality of SGSNs 607.
The SGSN 607 transfers the data of the MBMS contents to a corresponding RNC 609 on a service basis using the IP 610. The IP 610 supports a multicast function capable of transferring the same contents from one SGSN 607 to a plurality of RNCs 609 and also a unicast function capable of transferring the contents to one RNC 609. The RNC 609 transfers the MBMS data to a Node-B 611 through an interface 612. The Node-B 611 transfers the MBMS data to corresponding pieces of UE 613 using a Uu interface 614, which is an air interface.
FIG. 7 is a flow chart illustrating a signal processing procedure of a mobile communication network when a broadcast service of the conventional MBMS is provided. Referring to FIG. 7, a broadcast service of an MBMS is activated in response to a service delivery request from at least one service provider 601. Thus, at step 701, the BM-SC 602 receives the service delivery request from the service provider 601. At step 702, the BM-SC 602 receiving the service delivery request carries out charging and authentication procedures for the service provider 601 and then receives MBMS contents from the service provider 601. At step 703, radio access bearers for the broadcast service are configured in a CN (Core Network) to transfer the MBMS data to the RNC 609. The configuration of the radio access bearers for the broadcast service includes a procedure for setting up a multicast connection between the BM-SC 602 and the GGSN 605, a GTP connection between the GGSN 605 and the SGSN 607, and an IP multicast connection between the SGSN 607 and the RNC 609. Connection protocols between elements are based on the protocol architecture illustrated in FIG. 6. At step 704, radio bearers for the broadcast service are configured in the RNC 609. The radio bearers for the broadcast service are coupled between the RNC 609 and Node-Bs 611 to deliver the MBMS to pieces of UE 613. At the time of configuring the radio bearers, a common radio channel between the Node-B 611 and UE 613 is simultaneously set up After configuring the radio access bearers between the BM-SC 602, the GGSN 605, and the SGSN 607, in the CN and configuring the radio bearers in the RNC 609, at step 705, the MBMS data scheduled by the BM-SC 602 begins to be broadcast to the entire service area.
FIG. 8 is a flow chart illustrating a signal processing procedure of the UE when a broadcast service of the conventional MBMS is provided. Referring to FIG. 8, if the UE 613 selects a broadcast service of the MBMS at step 801, the UE 613 obtains parameters for at least one corresponding broadcast channel to receive the broadcast service in step 802. Alternatively, broadcast channel parameters received and stored in a procedure of enabling the UE 613 to recognize a cell, can be used. Also, the UE 613 can use broadcast channel parameters received from the Node-B 611 when it selects the broadcast service of the MBMS. In step 803, the broadcast channel is configured using the parameters obtained from the above-described procedure. If the broadcast channel is configured, the UE 613 receives data of the broadcast service of the MBMS through the configured broadcast channel in step 804.
FIG. 9 is a flow chart illustrating a signal processing procedure of a mobile communication network when a multicast service of the conventional MBMS is provided. Referring to FIG. 9, if the BM-SC 602 receives a multicast service delivery request from at least one service provider 601, the multicast service is activated at step 901. At step 902, the BM-SC 602 provides the multicast service to pieces of UE 613 after carrying out charging and authentication procedures for the service provider 601 requesting the multicast service delivery. At step 903, it is determined whether a service request corresponding to the multicast service delivery is received from the UE 613. The multicast service of the MBMS is different from the broadcast service in that the multicast service is provided to the UE 613 in response to the service request from the UE 613.
At step 903, if the service request is not received from the UE 613, a current state is maintained. Otherwise, if the service request is received from the UE 613, the UE 613 is authenticated in step 904. That is, it is determined whether the UE 613 has a right to receive the multicast service. The SGSN 607 carries out authentications for pieces of the UE 613. If the UE authentication has been completed, the SGSN 607 determines, at step 905, whether a connection for the multicast service of the MBMS has been set up.
If the connection for the multicast service is not set up, radio access bearers for the multicast service are configured in the CN at step 906. The configuration of the radio access bearers for the multicast service includes an IP connection between the BM-SC 602 and the GGSN 605, a GTP connection between the SGSN 607 and the GGSN 605, and an IP multicast connection between the SGSN 607 and the RNC 609. At step 907, radio bearers for an Iub interface and a Uu interface between the RNC 609 and the UE 613 for the multicast service of the MBMS are configured in the RNC 609.
If it is determined that the connection has been configured at step 905 or the radio bearers have been configured at the above steps 906 and 907, the requested multicast service is set up and then the SGSN 607 confirms the UE's service request at step 908. The SGSN 607 transfers information associated with a channel for receiving data of the multicast service of the MBMS. At step 909, the multicast service of the MBMS is provided to the pieces of the UE 613 authorized from the BM-SC 602.
FIG. 10 is a flow chart illustrating a signal processing procedure of the UE when a multicast service of the conventional MBMS is provided. Referring to FIG. 10, if the UE 613 selects the multicast service of the MBMS at step 1001, the UE 613 transfers a multicast service request to a mobile communication network at step 1002. At step 1003, the UE 613 receives confirmation information from the mobile communication network in response to the multicast service request. At this time, the UE 613 receives, from the mobile communication network, information necessary for receiving data of the multicast service. At step 1004, the UE 613 configures at least one multicast channel for receiving the multicast service of the MBMS using the received information. At step 1005, the UE 613 provides a user with the data of the multicast service of the MBMS through the configured multicast channel.
FIG. 11 illustrates communication protocol architecture of the UTRAN including the RNC 609 and the Node-Bs 611 illustrated in FIG. 6. Referring to FIG. 11, MBMS information 1101 in a U-plane from the BM-SC 602 is transferred to an MBMC-SAP (Multimedia Broadcast/Multicast Control-Service Access Point) 1102 coupled to the RNC 609 through the Iu interface 610 using IP multicast. The MBMS information 1101 is provided from the BM-SC 602. The MBMC-SAP 1102 transfers the MBMS information 1101 to an MBMC layer 1103 coupled to a corresponding cell. The MBMC layer 1103 corresponds to one cell and is responsible for the MBMS in the corresponding cell. The MBMS information 1101 received from the BM-SC 602 is stored in the MBMC layer 1103 of the corresponding cell. The MBMC layer 1103 requests an RRC layer 1104 controlling radio resources of the RNC 609 to set up or change radio channels through a CMBMC-SAP (Control MBMC-Service Access Point) 1105. To request the channel setup or change, the MBMC layer 1103 must consider a transmission rate of MBMS information to be broadcast/multicast in the corresponding cell, broadcast/multicast timing, a priority of a corresponding service, the number of rebroadcasts/remulticasts, a repetition period, etc. The RRC layer 1104 determines whether the radio channels can be set up or changed in response to the request from the MBMC layer 1103. If the radio channels can be set up or changed, the RRC layer 1104 sets up an RLC (Radio Link Control) layer 1107, a MAC-c/sh layer 1109, and a Cell_PHY (Cell_PHYsical) layer 1112, which is a physical layer of a corresponding cell through a C-SAP (Control-Service Access Point) 1106. However, if the RRC layer 1104 determines that it is difficult for the radio channels for the MBMS to be set up or changed because of insufficient radio resources, it notifies the MBMC layer 1103 of unsuccessful radio channel setup or change. The MBMC layer 1103 notifies the BM-SC 602 of the unsuccessful radio channel setup or change, thereby enabling the BM-SC 602 to stop a corresponding MBMS or adjust a transmission rate of the MBMS information. On the other hand, the MBMC layer 1103 schedules the MBMS information by considering the transmission rate, the broadcast/multicast timing, the number of rebroadcasts/remulticasts, the repetition period, etc., and then transfers the MBMS information to the RLC layer 1107 in the UM.
The MBMS information received from the MBMC layer 1103 is segmented into RLC protocol data units having a predetermined size by the RLC layer 1107. The RLC protocol data units are transferred to the MAC-c/sh layer 1109 through a CCTH 1108, which is a logical channel, by the RLC layer 1107. The MAC-c/sh layer 1109 transfers the RLC protocol data units to the Cell_PHY layer 1112 of a corresponding cell. Like the CBS, the MBMS is provided through a common channel. Thus, the RLC protocol data units for the MBMS are transferred from the MAC-c/sh layer 1109 to the Cell_PHY layer 1112 of the corresponding cell using an FACH 1111, which is a common transport channel.
The Cell_PHY layer 1112, which corresponds to each cell, performs channel coding, rate matching, interleaving, and modulation for the RLC protocol data units distributed by the MAC-c/sh layer 1109, maps the FACH to an S-CCPCH 1113 being a physical channel, and transmits the RLC protocol data units to a radio channel. Conceptually, the mapping to the physical channel means that the RLC protocol data units are transmitted through the Uu interface (radio channel) 614.
FIG. 12 illustrates communication protocol architecture of UE for providing the conventional MBMS corresponding to the configuration illustrated in FIG. 11. Referring to FIG. 12, a signal from the Node-B 611 is transmitted to a UE_PHY layer 1203 of the UE through an S-CCPCH 1202 of the Uu interface 614, which is the air interface. The UE_PHY layer 1203 performs demodulation, deinterleaving, and channel decoding for the received signal, produces data of an FACH 1204 from the received signal, and transfers the data of the FACH 1204 to a MAC-c/sh layer 1205.
As described above, the data is not transferred to a MAC-d layer 1206 responsible for a dedicated channel in the MBMS. The MAC-c/sh layer 1205 transfers RLC protocol data units for MBMS to an RLC layer 1208 responsible for a CTCH 1207 being a corresponding logical channel. The RLC layer 1208 associates the RLC protocol data units having the predetermined size received from the RLC layer of a transmitting side to generate original MBMS information and then transfers the MBMS information to an MBMC layer 1209. The MBMC layer 1209 transfers the MBMS information to a higher layer through an MBMC-SAP 1210 as indicated by a reference numeral 1211. Also, the UE 613 performs a series of control operations for the MBMS as in the RNC 609. That is, an RRC layer 1212 of the UE 613 controls the MBMC layer 1209 through the CMBMC-SAP 1213. Further, the RLC layer 1208, the MAC-c/sh layer 1205 and the UE_PHY layer 1203 are controlled through corresponding C-SAPs 1214 coupled to the RRC layer 1212.
FIG. 13 illustrates a detailed configuration and functions of the MBMC layers 1103 illustrated in FIG. 11. Referring to FIG. 13, the MBMS information transmitted from the BM-SC 602 is input into the MBMC-SAP 1102 and then distributed or transferred to MBMC layers corresponding to all cells included in the entire service area by the MBMC-SAP 1102. The MBMS information is transferred from an MBMC layer 1103 of each corresponding cell to a controller 1304. If the controller 1304 considers information associated with a transmission rate of the MBMS information, the broadcast/multicast timing, and a priority, from the BM-SC 602 and determines that radio channels must be prepared (i.e., either set up or changed), it requests the RRC layer 1104 to set up or change the radio channels through the CMBMC-SAP 1105. The operation of the RRC layer 1104 is the same as described in FIG. 11. Under the control of the controller 1304, the MBMS information stored in data storages 1307 is transferred to schedulers 1308. The schedulers 1308 schedule the MBMS information and then the scheduled MBMS information is transferred to the RLC layer 1107 based on the UM 1310 through transmission buffers 1309.
The above-described MBMC layer 1103 illustrated in FIG. 13 is different from the BMC layer 303 for the CBS illustrated in FIG. 4. That is, the BMC layer 303 allows a single CTCH in each cell and supports a simple message-type service, while the MBMC layer 1103 supports the MBMS. Thus, the MBMS needs a plurality of broadcast channels and a plurality of multicast channels on a cell basis and must support a transmission rate higher than the CBS. Moreover, the data storages 1307 must store service information on a service basis, and the data storages can store large-capacity data in comparison with the BMC layer 303. The schedulers 1308 must carry out respective service scheduling functions corresponding to the number of services supported in a corresponding cell. To transmit the service information to RLC layers 1311 on the service basis, the MBMC layer must include the transmission buffers 1309 corresponding to the number of services supported in a corresponding cell. To support a plurality of MBMSs, the controller 1304 must carry out more extended functions than the BMC layer 303.
The broadcast service of the MBMS simultaneously transmits data to a plurality of cells according to a defined service area. Thus, when the MBMC layer 1103 is constructed as illustrated in FIG. 13, there is a problem in that the MBMC layer 1103 of each cell repeatedly stores the same large-capacity data having a high-speed transmission rate. Similarly, there is a problem in that each cell repeatedly stores the same large-capacity data in the multicast service. For this reason, in the UTRAN, storage devices may be inefficiently utilized and the same broadcast/multicast between cells cannot be performed because respective cells individually perform MBMS scheduling and transmission. In particular, a real-time streaming service must simultaneously provide cells with the same high-speed service. Thus, the architecture of an independent cell may cause unnecessary repetition of operations. Since broadcast and multicast timings in respective cells are different, the continuous service cannot be ensured and a QoS (Quality of Service) can be degraded, from a user's perspective, when a handover is carried out in an overlap area between cells.